Re: [R] problem in Krig function of "Fields" package

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Wed 20 Jul 2005 - 18:56:00 EST

My guess is that you have two data points which are very close together. The normal way out is to included a nugget effect in your model, but it can also be appropriate to leave out one of a pair of points.

On Tue, 19 Jul 2005, orkun wrote:

> hello
>
> I try to build DEM using Krig function of fields package.
> And I get this error message.
> here is the procedure I followed:
>
> > dt<-read.table("/usr/local/bartin/stat/topostat1",header=F,sep="|")
> > names(dt) <-c("x","y","z")
> > coord<-cbind(dt$x,dt$y)
> > elevation<-cbind(dt$z)
> > fit1<-Krig(coord,elevation,cov.function=exp.cov,scale.type="range")
> [1] "condition number is 907405545.878743"
> Error in Krig(kord, el, cov.function = exp.cov, scale.type = "range") :
> Covariance matrix is close
> to
> singular
>
> here is the structure of my data:
>
> `data.frame': 3911 obs. of 3 variables:
> $ x: num 50139 50169 50214 50223 50227 ...
> $ y: num 4592999 4593322 4593054 4593151 4593246 ...
> $ z: int 320 320 320 320 320 320 320 320 320 320 ...
>
> what do you suggest to solve the problem ?
>
> kind regards
>
>
>
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-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Wed Jul 20 19:07:20 2005

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